The invention relates to a process for preparing a peracid, perester or diacylperoxide, a hydroxyperacid, hydroxyperester, and hydroxydiacylperoxide obtainable by said process, and the use of said hydroxyperoxides.
Peracids, peresters, and diacylperoxides are commercially important compounds and are used in bleaching, oxidation and/or epoxidation reactions (e.g. m-chloroperbenzoic acid) and/or as chain transfer agents and/or initiators for the radical (co)polymerization of (ethylenically unsaturated) monomers into polymers, e.g., (meth)acrylic resins, polyethylenes, polyvinylchlorides, polystyrenes, and copolymers thereof. These peroxides are also used for the modification of said polymers, e.g., grafting of monomers onto polymers, degradation or molecular weight reduction of polymers, and cross-linking. They may also be used for curing unsaturated polyesters. These peroxides can be used as such or in the form of a solution, emulsion or suspension containing the peroxide. Various methods of synthesis of the aforementioned peroxides are known in the art. Most of the reported methods and in particular the commercial routes involve the use of an acid chloride or an anhydride such as acetic anhydride or phthalic anhydride and sometimes a solvent.
These prior art methods suffer from the disadvantage that acid chlorides are expensive starting materials. Furthermore, some of the acid chlorides which would have to be used for the synthesis of the peroxides in accordance with the present invention have a very bad smell or have no EINECS (Europe), ELINCS (Europe), ENCS (Japan), and/or TSCA (United States) registration, which of course limits their use on a technical scale. Further, functionalized carboxylic acids of which the functional group reacts with an acid chloride group cannot be converted into the corresponding peroxides via the acid chloride route either. The use of anhydrides has the drawback that one equivalent of the corresponding acid is formed. Hence, this route is unattractive if the use of an expensive carboxylic acid is required.
For these reasons there is a need in this art for an alternate, preferably improved method of preparing peracids, peresters, diacylperoxides, and functionalized derivatives thereof.
We have found a new, commercially attractive process for preparing peracids, peresters, diacylperoxides, and functionalized derivatives thereof, which process does not suffer from the above-mentioned disadvantages.
The present invention generally relates to a process for preparing a peracid, perester or diacylperoxide, a hydroxyperacid, hydroxyperester, and hydroxydiacylperoxide obtainable by said process, and the use of said hydroxyperoxides. The process according to the present invention is characterized in that a mixed anhydride of specific formula is contacted with a hydroperoxide of formula of specific formula in the presence of a base, provided that if the hydroperoxide is an xcex1,xcex1xe2x80x2-dihydroperoxyperoxide, the reaction is not carried out in an inert two-phase solvent system comprising a polar solvent and an apolar solvent.
As previously described, the present invention generally relates to a process for preparing a peracid, perester or diacylperoxide, a hydroxyperacid, hydroxyperester, and hydroxydiacylperoxide obtainable by said process, and the use of said hydroxyperoxides. The process according to the present invention is characterized in that a mixed anhydride of formula R1[C(O)OC(O)OR2]n or [R3C(O)OC(O)O]pR4 is contacted with a hydroperoxide of formula R5[OOH]m in the presence of a base, wherein
R1 represents a mono-, di-, tri- or tetravalent C1-C19 hydrocarbon group,
optionally containing one or more hetero atoms,
n is 1-4,
R2 represents a C1-C20 hydrocarbon group, optionally containing one or more hetero atoms,
R3 represents a C1-C19 hydrocarbon group, optionally containing one or more hetero atoms,
R4 represents a di-, tri- or tetravalent C1-C20 hydrocarbon group, optionally containing one or more hetero atoms,
p is 2-4,
R5 represents hydrogen or a mono- or divalent C3-C18 tertiary alkyl or C2-C20 acyl group, in which the tertiary alkyl or acyl group may optionally contain one or more hetero atoms,
m is 1 or 2, and
if R5 represents hydrogen, m is 1,
provided that if the hydroperoxide is an xcex1,xcex1xe2x80x2-dihydroperoxyperoxide, the reaction is not carried out in an inert two-phase solvent system comprising a polar solvent and an apolar solvent.
In Applicant""s non-prepublished International Patent Application No. PCT/EP99/02643xe2x80x94later published as WO 99/52864xe2x80x94a process for preparing inter alia monoperoxy esters is described comprising reacting an xcex1,xcex1xe2x80x2-dihydroperoxyperoxide (referred to in the publication as a type-3 ketone peroxide) with a reactive carbonyl compound, which may be a mixed anhydride, in an inert two-phase solvent system comprising a polar solvent and an apolar solvent. The xcex1,xcex1xe2x80x2-dihydroperoxyperoxides described therein are of the formula HOOC(Ra)(Rb)OOC(Ra)(Rb)OOH, wherein Ra and Rb are independently selected from the group consisting of hydrogen and C1-C20 alkyl, C3-C20 cycloalkyl, C6-C20 aryl, C7-C20 aralkyl, and C7-C20 alkaryl groups, or Ra and Rb form a C3-C12 cycloalkyl group, which groups may include linear or branched alkyl moieties, and each of Ra and Rb may optionally be substituted with one or more groups selected from hydroxy, alkoxy, linear or branched alkyl, aryloxy, halogen, ester, carboxy, nitrile, and amido groups.
The present invention further relates to new hydroxyperacids, hydroxyperesters, and hydroxydiacylperoxides obtainable by the process defined above. Said hydroxyperoxides are further described below.
For illustrating the process in accordance with the present invention, the following reaction schemes are presented:
R1C(O)OC(O)OR2+HOOH gives R1C(O)OOH, a peracid
R1C(O)OC(O)OR2+HOOH gives R1C(O)OOC(O)R1, a diacylperoxide
R1C(O)OC(O)OR2+tert-alkylOOH gives R1C(O)OOtert-alkyl, a perester
R1C(O)OC(O)OR2+acylOOH gives R1C(O)OOacyl, a diacylperoxide
R1C(O)OC(O)OR2+R5(OOH)2 gives R1C(O)OOR5OOH, a ketone peroxide
2 R1C(O)OC(O)OR2+R5(OOH)2 gives R1C(O)OOR5OOC(O)R1, a ketone diperester,
2 Tert-alkylOOC(O)R1C(O)OC(O)OR2+HOOH gives a diacylperoxide having perester groups: tert-alkylOOC(O)R1C(O)OOC(O)R1C(O)OOtert-alkyl.
In the process according to the present invention a mixed anhydride of formula R1[C(O)OC(O)OR2]n or [R3C(O)OC(O)O]pR4 is contacted with a hydroperoxide of formula R5[OOH]m in the presence of a base. Preferably, a mixed anhydride of formula R1[C(O)OC(O)OR]n is used in the process of the invention.
R1 represents a mono-, di-, tri- or tetravalent C1-C19 hydrocarbon group (i.e. n is 1-4), optionally containing one or more hetero atoms. R1 thus may contain 1, 2, 3 or 4 xe2x80x94C(O)OC(O)OR2 (mixed anhydride) groups. Preferably, n is 1 or 2, more preferably 1.
R1, R2, R3, R4, and R5 independently may contain one or more hetero atoms (although the group R5 does not form part of a mixed anhydride this aspect of its definition nevertheless is discussed here in this section of the application). Suitable hetero atoms include oxygen, nitrogen, and halogen atoms, with oxygen and halogen atoms being preferred. The one or more hetero atoms may form functional groups in addition to the mixed anhydride group such as an ether, hydroxy, alkoxy, aryloxy, carbonyl, carboxy (i.e. acid, ester), peroxyester, percarbonate, nitrile, or amido group. Preferred functional groups are ether, hydroxy, carbonyl, and carboxy groups. More preferred are hydroxy groups. Preferably, the halogen atom is a chlorine or bromine atom, more preferably a chlorine atom.
Preferably, R1, R2, R3, R4, and R5 independently only contain a single functional group. More preferably, R1, R3, and R5 independently contain one or more hydroxy groups, even more preferably one hydroxy group. These R groups independently may further contain other functional groups as described above. Still more preferably, R1, R3 and R5 independently only contain a hydroxy group as the sole functional group. Most preferably, R1 or R3 and R5 contain a single hydroxy group.
Suitable R1 groups include C1-C19 alkyl, C3-C19 cycloalkyl, C3-C19 cycloalkylalkyl, C6-C19 aryl, C7-C19 arylalkyl, and C7-C19 alkylaryl groups, optionally containing one or more hetero atoms as defined above, wherein the alkyl moieties may be linear or branched, saturated or unsaturated, and the aryl moieties may be substituted with one or more substituents or not. Preferred substituents are hydroxy groups, linear or branched C1-C4 alkyl groups, and halogen atoms, more preferably hydroxy groups, methyl groups, and chlorine atoms. Preferably, R1 represents a linear or branched C:4-C12 alkyl group or a C6-C12 aryl group, said alkyl and aryl groups optionally being substituted with a hydroxy group, a linear or branched C1-C4 alkyl group such as a methyl group or a halogen atom such as a chlorine atom.
The process in accordance with the present invention is particularly suitable for preparing hydroxyperacids, hydroxyperesters, and hydroxydiacylperoxides having a hydroxy group in R1 or R3, more in particular hydroxyperesters and hydroxydiacylperoxides having a hydroxy group in R1 or R3 and having a hydroxy group in R5.
Hence, the invention further relates to hydroxyperacids obtainable by the process described above wherein R1 or R3 represents a C1-C19 hydrocarbon group, optionally containing one or more hetero atoms, substituted with a hydroxy group, n, R2, R4, and p have the meaning defined above, R5 represents hydrogen, and m is 1. Preferably, said hydroxyperacid is substituted with a single hydroxy group.
The invention also relates to hydroxyperesters obtainable by the process described above wherein R1 or R3 represents a C3-C20 hydrocarbon group, optionally containing one or more hetero atoms, substituted with a hydroxy group, n, R2, R4, and p have the meaning defined above, R5 represents a mono- or divalent C3-C18 tertiary alkyl group, optionally containing one or more hetero atoms, optionally substituted with a hydroxy group, and m is 1 or 2, with the exception of (9Z, 12R) 12-hydroxy-9-octadeceneperoxoic acid 1,1-dimethylethyl ester, 4-[(1,3-dihydro-1-hydroxy-3-oxo-2H-inden-2-ylidene)methyl]benzenecarboperoxoic acid 1,1-dimethylethyl ester, 4-(2-hydroxypropoxy)-4-oxo-butaneperoxoic acid 1,1-dimethylethyl ester, (1-hydroxy-1-methylethyl)-butanediperoxoic acid bis(1,1-dimethylethyl)ester, 6-(2-hydroxyethoxy)-6-oxo-hexaneperoxoic acid 1,1xe2x80x2-(1,1,3-trimethyl-1,3-propanediyl)ester, and 3,4-dihydroxycyclohexenecarboperoxoic acid 1,1-dimethylethyl ester, with the proviso that said hydroxyperester does not contain a hydroxyphenyl moiety or a 2-hydroxypropyl group and the hydroxy group is not in the form of a carboxylic acid group.
Preferably, n is 1 or 2. Preferably, R1 or R3 represents a C3-C12 hydrocarbon group. Preferably, R5 represents a monovalent C3-C19 tertiary alkyl group, more preferably a monovalent C3-C12 tertiary alkyl group. It is preferred thatxe2x80x94apart from the perester groupxe2x80x94the hydroxy group is the only functional group present in the molecule. Particularly preferred hydroxyperesters are those which have a single hydroxy group in R1 or R3 as well as in R5.
The invention further relates to hydroxydiacylperoxides obtainable by the process described above wherein R1 or R3 represents a C1-C19 hydrocarbon group, optionally containing one or more heteroatoms, substituted with a hydroxy group, n, R2, R4, and p have the meaning defined above, R5 represents hydrogen or a mono- or divalent C2-C20 acyl group, said acyl group optionally containing one ore more hetero atoms, said acyl group optionally substituted with a hydroxy group, and m is 1 or 2, with the exception of benzoyl hydroxyacetylperoxide, with the proviso that said hydroxydiacylperoxide does not contain a hydroxyphenyl moiety.
Preferably, n is 1 or 2. Preferably, R1 or R3 represents a C1-C12 hydrocarbon group. Preferably, R5 represents a monovalent C1-C12 acyl group, more preferably a monovalent C2-C12 acyl group. Most preferably, R5 represents. hydrogen. It is preferred thatxe2x80x94apart from the diacylperoxy groupxe2x80x94the hydroxy group is the only functional group present in the molecule. Particularly preferred hydroxydiacylperoxides are those which have a single hydroxy group in both acyl moieties.
Peroxides containing an aromatic hydroxy group, e.g., 4-hydroxyperbenzoic acid, typically are not suitable for use in radical reactions. However, they may be used in other applications. In contrast, the corresponding hydroxyalkylaryl derivatives, for example, can be used in all applications listed above.
Typical examples of carboxylic acids from which the R1[C(O)Oxe2x80x94]n moiety of the mixed anhydride of formula R1[C(O)OC(O)OR2]n is derived (as described below) include monoacids (i.e. n is 1) such as acetic acid, chloroacetic acid, dichloroacetic acid, propanoic acid, 2-methylpropionic acid, 2-methylbutanoic acid, propenoic acid, acrylic acid, methacrylic acid, butanoic acid, 2-butenoic acid, 2-methyl-2-butenoic acid, 3-methyl-2-butenoic acid, 2,3-dimethyl-2-butenoic acid, 2-ethyl-2-butenoic acid, 3-phenylpropenic acid, 2,2-dimethylpropanoic acid, 2,2-dimethylbutanoic acid, 2,2-dimethylpentanoic acid, 2-ethylbutanoic acid, 3,5,5-trimethylhexanoic acid, 2-ethylhexanoic acid, neohexanoic acid, 2-pentenoic acid, 4-methyl-2-pentenoic acid, 2,3-dimethyl-2-pentenoic acid, 3,4-dimethyl-2-2-pentenoic acid, 2-hexenoic acid, 2,4-hexadienoic acid, neoheptanoic acid, 2-octenoic acid, 2-nonenoic acid, neodecanoic acid, octanoic acid, nonanoic acid, lauric acid, benzoic acid, 2-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 4-tert-butylbenzoic acid, 3-chlorobenzoic acid, 2,4-dichlorobenzoic acid, p-phenylenediacrylic acid, 3-benzoylacrylic acid, phenylacetic acid, phenoxyacetic acid, cyclohexanecarboxylic acid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 2-hydroxypentanoic acid, 3-hydroxypentanoic acid, 4-hydroxypentanoic acid, 5-hydroxypentanoic acid, 4-hydroxy-2-pentenoic acid, hydroxyacetic acid, 2-hydroxyisobutyric acid, 2-hydroxypropanoic acid, 2-hydroxyhexanoic acid, 6-hydroxyhexanoic acid, 8-hydroxyoctanoic acid, hydroxypivalic acid; diacids (i.e. n is 2) such as succinic acid, methylsuccinic acid, diglycolic acid, glutaric (i.e. pentanedioic)acid, 3,5,5-trimethylpentanedioic acid, hexanedioic acid, 3,5,5-trimethylhexanedioic acid, 2,4,4-trimethylhexanedioic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, 1,4-cyclohexanedicarboxylic acid, cyclohexane-1,4-diacetic acid, maleic acid, citraconic acid, itaconic acid, fumaric acid, oxalic acid, terephthalic acid, phthalic acid, and isophthalic acid, hydroxysuccinic acid; triacids (i.e. n is 3) such as citric acid, 1,2,4-benzenetricarboxylic acid, and 1,3,5-benzenetricarboxylic acid; and tetraacids (i.e. n is 4) such as 1,2,4,5-benzenetricarboxylic acid and ethylenediaminetetraacetic acid.
Mixtures of one or more carboxylic acids may also be used for preparing the mixed anhydride. It is further noted that for some of the above-mentioned functionalized carboxylic acids suitable precursors are commercially available, e.g., 6-hydroxyhexanoic acid or its alkali metal salt may be prepared from the corresponding lactone following methods known to a skilled person. Ethyl 3-hydroxybutanoate can be used to prepare sodium 3-hydroxybutanoate and without removal of ethanol, the sodium salt can be converted into a mixed anhydride as described below.
If a di-, tri- or tetravalent carboxylic acid is used as the starting material it is not necessary to convert all carboxylic acid groups. Hence, by using such higher carboxylic acids, carboxylic acid groups could be introduced into the peroxides in accordance with the present invention. Mono- and diacids are preferred.
R2 represents a C1-C20 hydrocarbon group, optionally containing one or more hetero atoms (see above). Preferably, R2 represents a C3-C8 alkyl or a C6-C12 aryl group, most preferably a C3-C4 secondary alkyl group or a phenyl group.
The xe2x80x94C(O)OR2 moiety of the mixed anhydride of formula R1[C(O)OC(O)OR2]n is derived from a halogen formate, preferably a chloroformate.
Typical examples of chloroformates include 1-methylpropyl chloroformate, 4-methylphenyl chloroformate, phenyl chloroformate, 3-methoxybutyl chloroformate, phenylmethyl chloroformate, 2-methylphenyl chloroformate, 1,3-dimethylbutyl chloroformate, 3,4-dimethylbutyl chloroformate, octyl chloroformate, ethyl chloroformate, 2-methylpropyl chloroformate, n-butyl chloroformate, 2-ethylhexyl chloroformate, 2-methyl-2-propenyl chloroformate, cyclohexyl chloroformate, 3,5,5-trimethylhexyl chloroformate, methyl chloroformate, 2-methoxyethyl chloroformate, 1-methylethenyl chloroformate, diethyleneglycol bis(chloroformate), 2-ethoxyethyl chloroformate, 4-methoxy carbophenyl chloroformate, 1-methylethyl chloroformate, pentyl chloroformate, hexyl chloroformate, n-propyl chloroformate, 2,2-dimethylpropyl chloroformate, 1,1-dimethylethyl chloroformate, 1-methylheptyl chloroformate, and mixtures thereof.
Particularly preferred and inexpensive chloroformates are isopropyl chloroformate, sec-butyl chloroformate, and phenyl chloroformate.
R3 represents a C1-C19 hydrocarbon group, optionally containing one or more hetero atoms (see above). R3 has the same (preferred) definitions as are described above for R1 in the case of a monovalent (i.e. n is 1) C1-C19 hydrocarbon group. The R3C(O)Oxe2x80x94 moiety of the mixed anhydride of formula [R3C(O)OC(O)O]pR4 is derived from a carboxylic monoacid and suitable examples have been described above. R4 represents a di-, tri- or tetravalent (i.e. p is 2-4) C1-C20 hydrocarbon group, optionally containing one or more hetero atoms (see above). The [xe2x80x94C(O)O]pR4 moiety of the mixed anhydride of formula [R3C(O)OC(O)O]pR4 is derived from a bis- tris- or tetra(halogen formate), preferably the corresponding chloroformate. Preferably, p is 2 and a bischloroformate is used in the invention process.
Typical examples of suitable bischloroformates include ethylene glycol bischloroformate, diethylene glycol bischloroformate, triethylene glycol bischloroformate, 2,2-dimethyl-1,3-propanediol bischloroformate, bisphenol A bischloroformate, 1,4-butanediol bischloroformate, 1,6-hexanediol bischloroformate, 1,4-cyclohexanedimethanol bischloroformate, and 3-methyl-1,5-pentanediol bischloroformate.
A preferred readily available bischloroformate is diethylene glycol bischloroformate.
A typical example of a trischloroformate is tris(chlorocarbonyloxymethyl)ethane and of a tetrachloroformate is tetra(chlorocarbonyloxymethyl)methane (i.e. pentaerythritol tetrachloroformate).
Typical examples of mixed anhydrides which can be used in the process according to the invention include 3-chlorobenzoyl 1-methyl-1-propyl carbonate, phenoxyacetyl 1-methyl-1-propyl carbonate, 6-hydroxyhexanoyl 1-methylethyl carbonate, 4-methylbenzoyl 1-methyl-1-propyl carbonate, and cyclohexylcarbonyl 1-methyl-1-propyl carbonate.
The mixed anhydride of formula R1[C(O)OC(O)OR2]n or [R3C(O)OC(O)O]pR4 may be prepared according to methods that are well-known to a person skilled in the art.
In a preferred embodiment of the invention processxe2x80x94which is described in more detail belowxe2x80x94the mixed anhydride used in the invention process is prepared in an aqueous medium. According to this embodiment, the mixed anhydride is prepared by reacting a carboxylic acid of formula R1[C(O)OH]n with a halogen formate, preferably a chloroformate of formula XC(O)OR2 or a bischloroformate of formula [XC(O)O]2R4, in the presence of a base in an aqueous medium, wherein R1, R2, R4, n, and p have the same meaning as defined above and X is a halogen atom. Suitable examples of carboxylic acids and halogen formates are described above.
The reaction can be carried out using means and equipment that are known to one of ordinary skill in the art. It can be carried out in a batch, semi-batch or continuous fashion.
It was found that the carboxylic acid should not be too acidic. For example, the mixed anhydride of oxalic acid (i.e. pKa1 of 1.23 and pKa2 of 4.19) could not be detected or isolated when prepared in an aqueous medium. Preferably, a carboxylic acid having a (first) pKa of 3 or higher, more preferably 4 or higher is used.
It is to be noted that in particular hydroxy-containing carboxylic acids, which are able to form a 5- or 6-membered ring lactone, are less suitable starting materials for making a mixed anhydride in an aqueous medium.
Any base can be used for making the mixed anhydride in an aqueous medium. Suitable bases include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide, sodium carbonate, sodium bicarbonate, sodium phosphate, sodium hydrogen phosphate, calcium oxide, magnesium oxide, and mixtures thereof. Preferably, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate or a mixture thereof is used as the base, most preferably sodium hydroxide or potassium hydroxide. Typically, an aqueous solution of the base is used.
Typically, the pH during the preparation of the mixed anhydride in an aqueous medium is kept at a value of 3 to 14, preferably 5 to 11, most preferably 6 to 9.
The molar ratio of carboxylic acid to halogen formate can vary over a wide range. Preferably, about equimolar amounts of carboxylic acid and halogen formate are used.
The preparation of the mixed anhydride in an aqueous medium can be carried out within a wide temperature range, typically from xe2x88x9225 o 75xc2x0 C. Preferably, the reaction is carried out at xe2x88x9210 to 40xc2x0 C., most preferably 0 to 20xc2x0 C.
Typically, the reaction time in a batch process ranges from 0.1 to 10 h. Suitably, the reaction time is from 0.5 to 3 reaction times generally are shorter.
Although the preparation of the mixed anhydride in an aqueous medium can be carried out without the use of a catalyst, it is advantageous to use one. Typically, a phase transfer catalyst is used as a suitable catalyst. Preferably, the phase transfer catalyst is a quaternary ammonium compound. Said quaternary ammonium phase transfer catalysts are known in the art. Typical examples include tetrabutylammonium bromide, benzyltrimethylammonium chloride, methyltricaprylammonium chloride, methyltributylammonium chloride, methyltrioctylammonium chloride, triethylbenzylammonium chloride, cocobenzyldimethylammonium chloride, and tetrabutylammonium hydrosulphate. However, tertiary amines such as triethylamine, trimethylamine, and N-methylmorpholine can also be used.
Typically, the quaternary ammonium phase transfer catalyst is used in an amount of 0.01 to 10 mole %, preferably 0.1 to 3 mole %, based on the amount of carboxylic acid.
R5 represents hydrogen or a mono- or divalent (i.e. m is 1 or 2) C3-C18 tertiary alkyl or C2-C20 acyl group, in which the tertiary alkyl or acyl group may optionally contain one or more hetero atoms as defined above. Preferably, R5 represents hydrogen or a monovalent C3-C18, more preferably C3-C10 tertiary alkyl group. The tertiary alkyl group may contain further branches, unsaturated groups such as alkynylene groups, and saturated or unsaturated rings such as cyclohexylene and phenylene groups. In the hydroperoxide of formula R5[OOH]m, the one or more hetero atoms may, in addition to forming functional groups as described above, also form peroxy or hydroperoxy groups.
If R5 is hydrogen, m is 1 and the hydroperoxide to be used in the invention process is hydrogen peroxide. Typically, an aqueous solution of hydrogen peroxide is used, for example, a 50 wt % aqueous solution of hydrogen peroxide.
Typical examples of tertiary hydroperoxides which can be used in the invention process include monohydroperoxides (i.e. m is 1) such as tert-butyl hydroperoxide, 1,1-dimethylpropyl (or tert-amyl)hydroperoxide, 1,1-dimethylbutyl (or tert-hexyl)hydroperoxide, 1-methyl-1-ethylpropyl hydroperoxide, 1,1-diethylpropyl hydroperoxide, 1,1,2-trimethylpropyl hydroperoxide, cumyl hydroperoxide, 1,1-dimethyl-3-hydroxybutyl (or hexylene glycol)hydroperoxide, 1,1-dimethyl-3-(2-hydroxyethoxy)butyl hydroperoxide, 1,1-dimethyl-3-(2-hydroxy-1-propyloxy)butyl hydroperoxide, 1,1-dimethyl-3-(1-hydroxy-2-propyloxy)butyl hydroperoxide, 1,1-dimethylpropenyl hydroperoxide, and 1,1,3,3-tetramethylbutyl hydroperoxide and dihydroperoxides (i.e. m is 2) such as 2,2-dihydroperoxypropane, 2,5-dimethyl-2,5-dihydroperoxyhexane, 2,5-dimethyl-2,5-dihydroperoxyhex-3-yne, 1,3-cyclohexylenedi(1-methylethylidenehydroperoxide), 1,4-cyclohexylenedi(1-methylethylidenehydroperoxide), 1,3-phenylenedi(1-methylethylidenehydroperoxide), and 1,4-phenylenedi(1-methylethylidenehydroperoxide).
Typical examples of hydroperoxides in which R5 represents an acyl group include perlauric acid, m-chloroperbenzoic acid, and perhexanoic acid.
Typical examples of hydroperoxides containing a second hydroperoxy group and a peroxy group are xcex1,xcex1xe2x80x2-dihydroperoxyperoxides of formula HOOC(Ra)(Rb)OOC(Ra)(Rb)OOH. Said peroxides are described in Applicant""s non-prepublished International Patent Application No. PCT/EP99/02643 and a description of the Ra and Rb groups is given above. These peroxides are also referred to as ketone peroxides.
Typical examples of hydroperoxides containing a second hydroperoxy group are gem-dihydroperoxides of formula HOOC(Ra)(Rb)OOH, wherein Ra and Rb have the meaning described above. Said peroxides are known in the art and have been described, for example, in Applicant""s WO 99/32442. Said peroxides are also prepared from ketones.
Suitable ketones that can be used for making said bishydroperoxides include acetone, methoxy acetone, methylchloromethyl ketone, methylbromomethyl ketone, methylethyl ketone, methyl n-propyl ketone, methylisopropyl ketone, methyl n-butyl ketone, methylisobutyl ketone, methyl tert-butyl ketone, methyl n-amyl ketone, methylisoamyl ketone, methylhexyl ketone, methylheptyl ketone, ethylpropyl ketone, ethylbutyl ketone, ethylamyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, isobutylheptyl ketone, 4-hydroxy4-methyl-2-pentanone, cyclohexanone, 2-methylcyclohexanone, 2,4,4-trimethylcyclohexanone, butyl levulinate, ethyl acetoacetate, methylbenzyl ketone, acetophenone (i.e. phenylmethyl ketone), and phenylethyl ketone.
Methods for the synthesis of the above-mentioned hydroperoxides are well-known in the art. Frequently, mixtures of peroxides are obtained which can be separated or used as such.
If possible, the tert-alkyl hydroperoxide is used in the process according to the present invention in the form of an aqueous solution, for example, 70 wt % aqueous tert-butyl hydroperoxide.
Specific examples of peroxides which can be prepared by the process according to the present invention include peracids such as m-chloroperbenzoic acid; peresters such as 2,5-bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane, tert-butylperoxy 2-ethylhexanoate, tert-butylperoxy m-chlorobenzoate, tert-butylperoxy o-methylbenzoate, tert-butylperoxy phenylacetate, 1,4-bis(tert-butylperoxycarbo)cyclohexane, 3-hydroxy-1,1-dimethylbutylperoxy 6-hydroxyhexanoate, 2,2,4,4-tetramethylbutylperoxy phenoxyacetate, di-tert-butylperoxy oxalate, tert-butylperoxy 2-chloroacetate, tert-butylperoxy cyclododecyloxalate, tert-butylperoxy n-butyloxalate, 1-hydroxyperoxy-1-methylpropyl, (1-methyl-1-phenylacetylperoxy)propyl peroxide; diperesters such as di((1-methyl-1-phenyl-acetylperoxy)propyl)peroxide, and 2,2-di(phenoxyacetylperoxy)-4-methylpentane; and diacylperoxides such as dicyclohexylcarbonylperoxide, di(4-methylbenzoyl)peroxide, lauroyl cyclohexylcarbonyl peroxide, and lauroyl 6-hydroxyhexanoyl peroxide.
Specific examples of new hydroxy-containing peroxides in accordance with the present invention include hydroxyperacids such as 3-hydroxyperbenzoic acid and 4-hydroxyperbenzoic acid; hydroxyperesters such as tert-butylperoxy 6-hydroxyhexanoate, tert-amylperoxy 6-hydroxyhexanoate, 3-(2-hydroxyethoxy)-1,1-dimethylbutylperoxy 6-hydroxyhexanoate, tert-butylperoxy 3-hydroxybutanoate, tert-amylperoxy 3-hydroxybutanoate, 3-hydroxy-1,1-dimethylbutylperoxy 3-hydroxybutanoate, 3-(2-hydroxyethoxy)-1,1-dimethylbutylperoxy 3-hydroxybutanoate, 3-hydroxy-1,1-dimethylbutylperoxy 4-hydroxybutanoate, 1,1-dimethylpropylperoxy 3-hydroxypentanoate, 1,1,4,4-tetramethylbutylperoxy 4-hydroxypentanoate, 3-hydroxy-1,1-dimethylbutylperoxy 5-hydroxypentanoate, cumylperoxy 6-hydroxyhexanoate, 1,1-dimethylpropylperoxy 8-hydroxyoctanoate, 3-hydroxy-1,1-dimethylbutylperoxy 12-hydroxylauroate, 3-hydroxy-1,1-dimethylbutylperoxy 10-hydroxydecanoate, 3-hydroxy-1,1-dimethylbutylperoxy 6-hydroxyhexanoate, 3-hydroxy-1,1-dimethylbutylperoxy 4-(hydroxymethyl)benzoate; and hydroxydiacylperoxides such as 2,5-dimethyl-2,5-di(6-hydroxyhexanoylperoxy) hexane, 1,3-di(1-methyl-1-(5-hydroxypentanoylperoxy)ethyl)cyclohexane, di(3-hydroxybutanoyl) peroxide di(4-hydroxybutanoyl)peroxide, di(2-hydroxypentanoyl)peroxide, di(3-hydroxypentanoyl)peroxide, di(4-hydroxypentanoyl)peroxide, di(5-hydroxypentanoyl)peroxide, di(hydroxyethanoyl)peroxide, di(2-hydroxyisobutanoyl)peroxide, di(2-hydroxypropanoyl)peroxide, di(2-hydroxyhexanoyl)peroxide, di(6-hydroxyhexanoyl)peroxide, di(8-hydroxyoctanoyl)peroxide, di(hydroxypivaloyl)peroxide, di(12-hydroxylauroyl)peroxide, di(10-hydroxydecanoyl)peroxide, di(4-(hydroxymethyl)benzoyl)peroxide, 6-carboxyhexaneperoxoic acid OO-(1,1-dimethylethyl) O-(4-hydroxybutyl)ester, bis(6-(4-hydroxybutyloxy)-6-oxohexanoyl peroxide, benzenecarboperoxoic acid 2-carboxy OO-(3-hydroxy-1,1-dimethylbutyl) O-(6-hydroxyhexyl)ester, and bis(2-(6-hydroxyhexyloxycarbonyl)benzoyl) peroxide.
Preferably, the hydroxyperester in accordance with the present invention is selected from the group consisting of tert-butylperoxy 6-hydroxyhexanoate, tert-amylperoxy 6-hydroxyhexanoate, 3-hydroxy-1,1-dimethylbutylperoxy 6-hydroxyhexanoate, 3-(2-hydroxyethoxy)-1,1-dimethylbutylperoxy 6-hydroxyhexanoate, tert-butylperoxy 3-hydroxybutanoate, tert-amylperoxy 3-hydroxybutanoate, 3-hydroxy-1,1-dimethylbutylperoxy 3-hydroxybutanoate, and 3-(2-hydroxyethoxy)-1,1-dimethylbutylperoxy 3-hydroxybutanoate. More preferably, the group consisting of tert-butylperoxy 6-hydroxyhexanoate, tert-amylperoxy 6-hydroxyhexanoate, and 3-(2-hydroxyethoxy)-1,1-dimethylbutylperoxy 6-hydroxyhexanoate.
Preferably, the hydroxydiacylperoxide in accordance with the present invention is selected from the group consisting of di(6-hydroxyhexanoyl)peroxide and di(3-hydroxybutanoyl)peroxide.
The process of the invention is carried out using means and equipment known to a person of ordinary skill in the art. It can be carried out in a batch, semi-batch or continuous fashion.
The process according to the present invention can be carried out in the presence or absence of an added reaction medium. It may be performed in an aqueous medium, in a mixture of water and an organic solvent, in an organic solvent, or in the absence of any water and organic solvent. In this last case, the mixed anhydride and the hydroperoxide react with each other in the absence of any added reaction medium, i.e. neat. Typical suitable solvents include ethers such as diethyl ether, esters, and optionally halogenated alkanes. Preferably, no organic solvent is used in the process according to the present invention, most preferably the reaction is carried out in an aqueous medium.
This most preferred embodiment has the advantage that no organic solvent is used. In addition, the organic phase can easily be separated from the aqueous phase using conventional separation techniques.
A further advantage is that the peroxide which is prepared in an aqueous medium can easily be transformed into an emulsion or suspension of the peroxide without separating the organic layer containing the peroxide from the water layer. This formulation then can be used directly in one or more of the above-described applications.
During the reaction one or, in the case of a di-, tri- or tetravalent R1 group or a divalent R5 group, more equivalents of a carbonate of formula xe2x88x92OC(O)OR2 or [xe2x88x92OC(O)O]pR4 are formed. When for example an aqueous sodium hydroxide solution is used as the base in the invention process (see below), the corresponding sodium carbonate is formed. This carbonate can be removed from the reaction mixture, i.e. the reaction products, by washing with water. If a pH lower than 7 is used for the reaction, the carbonate of formula xe2x88x92OC(O)OR2 or [xe2x88x92OC(O)O]pR4 typically decomposes to form the corresponding (di)alcohol and carbon dioxide. The preferred chloroformates yield alcohols which can be removed from the organic phase containing the peroxide by washing.
The invention process can be carried out within a wide range of molar ratios of mixed anhydride to hydroperoxide. Preferably, a small molar excess of hydroperoxide is used, i.e. typically 1 to 40, preferably 2 to 20 mole %.
Any base can be used for making the peracid, perester or diacylperoxide in accordance with the process of the present invention. Suitable bases include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide, sodium carbonate, sodium bicarbonate, sodium phosphate, sodium hydrogen phosphate, calcium oxide, magnesium oxide, and amines like pyridine, trimethylamine, and triethylamine, and mixtures thereof, alkali metal hydroxides being preferred. Preferably, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate, pyridine, trimethylamine, triethylamine or a mixture thereof, more preferably sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate or a mixture thereof, most preferably sodium hydroxide or potassium hydroxide is used. Typically, an aqueous solution of the base is used in the invention process.
Typically, the pH is kept at a value of 4 or higher, preferably 5 or higher, more preferably 6 or higher, most preferably 10 or higher.
The process according to the invention can be performed within a wide temperature range, typically of xe2x88x9225 to 75xc2x0 C. The reaction temperature is determined by the decomposition temperature of the peroxide formed during the process of the invention and the reactivity of the mixed anhydride and the hydroperoxide. Preferably, the reaction is carried out at a temperature in the range of xe2x88x925 to 50xc2x0 C., most preferably 0 to 30xc2x0 C.
The invention process typically is performed at atmospheric pressure.
Typically, the reaction time varies from 0.05 to 10 h. A suitable reaction time is from 0.5 to 4 h.
In a typical procedure, to a reaction vessel equipped with a turbine stirrer, a thermometer and a pH electrode/pH meter are added waterxe2x80x94optionally containing sodium chloride, which may increase the yield of the reaction-, the carboxylic acid, and optionally a quaternary ammonium phase transfer catalyst. The temperature and the pH are adjusted to the desired valuesxe2x80x94the pH preferably by dosing an aqueous sodium hydroxide solution. Then, the halogen formate and the basexe2x80x94preferably an aqueous sodium hydroxide solutionxe2x80x94are addedxe2x80x94preferably simultaneouslyxe2x80x94over a certain period of time while the temperature and the pH are kept at the desired values. After completion of the formation of the mixed anhydride, the hydroperoxide is added with control of the temperature and the pH. The reaction is allowed to proceed until about all of the mixed anhydride has reacted.
The work-up procedure depends on the type of peroxide being prepared. For peresters, the water layer is separated from the organic layer containing the peroxide and the organic layer is subsequently washed with an aqueous sodium sulphite solution, water, and/or an aqueous sodium chloride solution and then dried. In the case of diacylperoxides, the water layer is separated from the organic layer, e.g., by liquid/liquid separation or filtration, and the organic layer is washed with water and/or an aqueous sodium chloride solution and, in the case of a liquid peroxide, dried. For peracids, the water layer is acidified, and the organic layer is separated from the water layer, e.g., by liquid/liquid separation or filtration, washed with water and/or an aqueous sodium chloride solution, and then dried. Solid peroxides are isolated by filtration or centrifugation and may be recrystallized from a suitable solvent.
Typically, the nucleophilic attack of the hydroperoxide on the carboxylic acid carbonyl group of the mixed anhydride is not completely selective. As shown in the examples below, which are non-optimized experiments, yields typically range between 70 and 86%. Without wishing to be bound by any theory, Applicant believes that the selectivity is determined by steric hindrance and the inductive effects on the carboxylic acid and formic acid carbonyl groups, and that it can be steered to some extent by the appropriate selection of R groups. It was found that the best results in terms of yield and selectivity were obtained using isopropyl chloroformate and sec-butyl chloroformate.
The peracids, peresters, diacylperoxides, and hydroxyperoxides in accordance with the present invention may be formulated in a conventional way. To this end, the reader is referred to the state of the art, for example WO 99/32442.
The peroxides obtained by the process according to the present invention can be used in all applications mentioned above, e.g., the polymerization of monomers and/or the modification of these polymers and other polymers as described above, in the usual amounts and using conventional methods.
The hydroxyperesters and hydroxydiacylperoxides obtainable by the process of this invention are particularly suitable for use in (co)polymer modification reactions, e.g. the preparation of hydroxy-functionalized poly(meth)acrylates. Said acrylates may be used for example in high solids coating resins.